华北东部中生代构造体制转折峰期的主要地质效应和形成动力学探讨

Geological features of Mesozoic tectonic regime inversionin Eastern North China and implication for geodynamics

华北中生代构造体制转折始于 15 0～ 14 0Ma ,终于 110～ 10 0Ma ,峰期是 12 0～ 110Ma ,总体上是由挤压构造体制转化为伸展构造体制 ,由EW向转变为NNE向的盆岭构造格局。但是转折过程有复杂的细节和多次挤压与伸展的转变 ,边缘与克拉通内部、北缘与南 (东 )缘之间在时间和空间上也有一定的变化。南 (东 )缘的挤压构造以 2 30～ 2 10Ma为主 ,然后在 130～ 110Ma期间达到构造转折的剧变期。北缘则似乎表现出 2 30～ 2 10Ma和 180 ( 170 )～ 16 0 ( 15 0 )Ma两期挤压构造 ,130～ 110Ma是构造转折的峰期。盆地的演化有多样性 ,燕山地区前晚侏罗世时期呈现出北东东向褶皱逆冲带与挤压挠曲盆地带相邻并存的盆山结构 ;而后晚侏罗世时期呈现出北北东向裂谷盆地与断隆相间的盆岭结构 ;晚侏罗世后时期则呈现出北东—北北东向盆地与“活动”断隆相间 ,并受北东东向褶皱逆冲带控制的盆山结构。大别山南北隆升历史完全不同。深部结构的研究表明 ,华北东部的岩石圈在古生代末期已有减薄表现 ,在中生代急剧减薄 ,地幔和下地壳发生大规模置换 ,至 130～ 110Ma到达顶峰。新生代以来又有加厚的趋势。中生代构造转折不具典型造山带特征 。

The time span of Mesozoic tectonic regime inversion in eastern North China is from 150～140 Ma to 110～100 Ma, with a peak stage at 120～110 Ma. The basin-range framework, in general, was changed from EW-trending to NE-NNE-trending, and a compressive tectonic regime was changed to an extensional tectonic regime. However, the Mesozoic tectonic inversion process was complicated, showing multi-stage inversion of compression and extension. There were certain variations both in time-space and along the margins versus within the craton. In the south (east) of the craton, a compressive structural event occurred mainly in 230～210 Ma, and the peak stage of extensional tectonic inversion was in 130～110 Ma. In the north, two compressive events occurred in 230～210 Ma and 180(170)～160(150) Ma, respectively, and a peak stage of extensional tectonic inversion was also in 130～110 Ma. The evolution of Mesozoic basins shows diversity. In Yanshan area, the pre-Late Jurassic basins belong to compressive-flexure coexisted with NEE-trending thrust zones. The Late Jurassic NEN-trending rift basins coexisted with uplift zones. The post-Late Jurassic basins trending NE-NEN coexisted with active uplift zones and controlled by NEE-trending thrust zones. The south and north Dabieshan units have different uplifting histories. The study of deep-seated structure shows that the lithosphere of the eastern North China had been drastically thinned and a massive replacement of mantle with lower crust had occurred in the Mesozoic, which attained their extremes in 130～110 Ma. The Mesozoic tectonic regime inversion shows no characteristics of orogenic belt, which is probably related to the large-scale upwelling of the mantle under the joint grip of the surrounding blocks.